High pressure wellhead assembly



June 9, 1964 E. D. YETMAN ETAL 3,135,363

HIGH PRESSURE WELLHEAD ASSEMBLY 2 Sheets-Sheet 1 Filed May 2, 1961 ss 5gas FIG.

VINVENTORSI L. G. OTTEMAN E. D. YETMAN June 9, 1964 E. D. YETMAN ETAL3,136,363

HIGH PRESSURE WELLHEAD ASSEMBLY Filed May 2, 1961 2 Sheets-Sheet 2INVENTORSZ L. G. OTTEMAN E. D. YETMAN HEIR AGENT United States PatentOffice 3,136,363 Patented June 9, 1964 3,136,363 HIGH PRESSURE WELLHEADASSEMBLY Edward D. Yetman and Lloyd G. Otteman, Houston, Tex., assignorsto Shell Oil Company, New York, N.Y., a corporation of Delaware FiledMay 2, 1961, Ser. No. 107,257 Claims. (Cl. 16691) This invention relatesto equipment used at the top of an oil or gas well and pertains moreparticularly to a wellhead assembly adapted to be secured to the top ofa well casinghead for controlling the fluid flow from the well whileproviding apparatus whereby substances such as chemicals as well assubstances having a physical structure such as tools, instruments orother devices can be made to enter a high pressure well from a lowerpressure flowline outside the well.

A recent development in the drilling and completion of oil and gas wellshas been the, drilling and completion of underwater wells wherein thewellhead assembly and casinghead may be positioned hundreds of feetbelow the surface of the water at an offshore location, one such methodbeing described in copending patent application, Serial No. 830,538,filed July 30, 1959. In order to carry out maintenance and otheroperations on wells wherein the wellhead assembly is positioned aconsiderable distance below the surface of the water, methods forcarrying out these operations have been developed. One of these methodshas been classified as a through-the-flowline well maintenancetechnique. For performing the required operations involved inmaintaining wells in this manner, various tools and other devices whichare capable of being pumped into and out of the well bore through theproduction or fluid flowline have been developed. Since thesemaintenance tools and other devices must be pumped into a Well bore, andsince they are not able to pass around right angle bends in the normalwellhead assembly, a new type of a wellhead has been developed asdescribed in copending patent application, Serial No. 834,095, filedAugust 17, 1959, now Patent No. 3,101,118.

Although a wellhead assembly has been developed into which tools andother devices may be pumped through the flowlines and into the well,well servicing operations have been hampered in many cases due to thefact that the flexible flowlines, which are generally used fromunderwater wells, do not withstand the high pressures encountered inmany wells. For wells up to around 5,000 p.s.i. it is possible for thepresent flexible flowlines to take the full well pressure in the line.Since many wells may have pressures up to 10,000 p.s.i., it may be seenthat any attempt to handle them in a 5,000 p.s.i. flowline would lead torupture of the flowline.

It is, therefore, a primary object of the present invention to provide awellhead assembly provided with a wellhead control manifold systemwhereby tools, instruments and other substances may be caused to enter ahigh pressure well from a low pressure flowline without exposing the lowpressure flowline to the high pressures of the well.

A further object of the present invention is to provide a wellheadassembly having a wellhead control manifold system whereby flow controlchokes employed to reduce well pressures to acceptible flowlinepressures can be changed from a remote location by pumping the chokes toand from the wellhead through the flowline without exposing the lowpressure flowline to the high well pressures.

Another object of the present invention is to provide a wellheadassembly including a wellhead control manifold system whereby slugs ofvarious chemicals may be injected into the well from a low pressureflowline into a high pressure well.

These and other objects of the present invention will be understood fromthe following description taken with regard to the drawing, wherein:

FIGURE 1 is a schematic view illustrating many of the components whichmay be arranged as an underwater wellhead assembly for carrying out theobjects of the present invention; and,

FIGURES 2 and 3 are alternative arrangements of dual flowlines at thetop of a wellhead.

Although the wellhead assembly of the present invention is describedhereinbelow with regard to a well having two parallel strings ofproduction tubing suspended therein, it will be readily apparent thatthe present wellhead assembly can be modified so as to be employed onwells having a single tubing string or two concentric tubing strings, oron wells having three or more parallel strings of tubing suspendedwithin a well casing.

Referring to FIGURE 1 of the drawing, a casinghead closure member 11having an annular sealing element 12 carried on its outer surface isshown as positioned on the inner sloping seating surface 13 at the topof a casinghead 14, thus closing the casinghead 14 in a fluidtightmanner. The casinghead closure member 11 is provided with a pair ofvertical conduits centrally disposed in side-by-side arrangement andextending vertically down through the casinghead closure 11 in registerwith a pair of strings of production tubing (not shown) suspended withinthe well. For purposes of illustration, it may be considered that thewell casinghead 14 and the wellhead assembly of the present inventionare mounted on an offshore well and are positioned underwater.

Fixedly secured to the top of the casinghead closure member 11, as bybolts 17, is a master valve 18 having dual gates or closure elements 19and 20 by which the well may be shut in upon closing of both gates ofthe valve 18. Preferably, a second master valve 18a having dual closureelements 19a and 20a is mounted above the master valve 18 as a safetyprecaution. The valves 18 and 18a are preferably of theremotely-controlled fullopening type, that is, the gate or plugcontrolling the flow within the valve is of a type that, when opened,furnishes a straight passageway through the valve of a diametersubstantially equal to that of the vertical conduits 15 and Fixedlysecured to the top of the master valve 18a is a Y spool piece 21 havinga pair of vertical conduits 22 and 23 therethrough in register, throughmaster valves 18 and 18a, with the vertical conduits 15 and 16 in theeasinghead closure member 11.

Smoothly curving from the vertical conduits 22 and 23 of the Y spoolpiece 21 are a pair of side conduits 24 and 25 which branch upwardly andoutwardly through the side Wall of the spool piece 21. These branchingside conduits 24 and 25 may be in the form of independent nipples, aswill be described hereinbelow with regard to FIGURE 2, when it is notdesired to employ any vertical conduits22 and 23. The curvature of theside conduits or nipples 24 and 25 depends, to some extent, upon thelength and the flexibility of the tools, instruments or other devices tobe circulated down into the well through the side conduit. Thus, withpresently developed tools, the radius of curvature of the side conduitsor nipples 24 and 25 may be on the order of five feet.

Each of the side conduits or nipples 24 and 25 are provided with flanges26 and 27, or other coupling means,

for connecting a pair of control valves 30 and 31 to the along the oceandoor to the shore or to some tank positioned offshore for collection orseparation purposes. In the event that the sections of productionflowlines 32 and 33, directly connected to the control valves 39 and 31are metal, they should be smoothly curved in an arc of a radius not lessthan that which would permit objects to be circulated therethrough intothe well. it is quite apparent that whether the flowlines 32 and 33 areof a rigid or flexible material, all curves therein must have a minimumradius of not less than that required for circulation of objectstherethrough.

From the construction of the present wellhead assembly, it may be seenthat tools and instruments may be readily circulated down through theproduction flowline 32, the side conduit or nipple 24, and thencethrough the vertical conduits 22 and 15, down into a low pressure well.However, on circulating a tool (not shown) up from the bottom of thewell, by reversing the circulation of fluid through conduits 32 and 33,the tool would be driven up the vertical conduit and conduit 22 andbecome lodged therein rather than sweeping out the side conduit 24 andthence through the production flow line 32. It, therefore, has beenfound necessary to provide the vertical conduits 22 and 23 o f the Yspool piece 21 with diverting plugs 34 and 35 which are removablypositioned therein to close the vertical conduits 22 and 23 above theside conduits 24 and 25. The lower ends 36 and 37 of the tool divertingplugs 34 and35, respectively, are shaped in a manner such that the lowertapered face thereof forms a continuation of the inner wall of thesmoothly curved side conduits 24 and 25. That is, the lower end 37 ofplug 35 is curved in amanner so as to bend in an arc of the same radiusas the side conduit 25, while at the same time having a concave facemachined, cut, or formed so that a concave portion is curved in a radiusequal to that of the inside of the conduits 24 and 25.

The tool diverting plugs 34 and 35 are provided with fishing heads 40and 41 by which the plugs 34 and 35 may be removed, as by means of awire line fishing tool. The tool diverting plugs 34 and 35 are alsoprovided with suitable retractable latching or stop means in a mannerwell known to the art for fixedly positioning the plugs in place so thatthe Well pressure does not force them upwardly out of alignment with theside conduits 24 and 25. Retractable latching means 42 and 43 are wellknown to the art and are used on many wire line tools. The latches 42and 43 may be withdrawn or set in any suitable manner,

as by manipulation of the fishing heads 40 and 41 with wire line orother tools. If desired, the plugs may also be provided with O'-ringseals 44 and 45.

As described in copending patent application, Serial No. 834,095, filedAugust 17, 1959, suitable guide means are provided on the tool divertingplug 35 and on the interior wall of the vertical bore 23 of the Y spoolpiece 21 above the side conduit for orienting the lug to its properposition within the vertical bore 23 of the Y spool piece 21. Preciselocation of the plug within the conduit 23 is necessary in order to beable to circulate tools through the. side conduit 25. If a wellhead ofthe present invention were to be employed above the surface of thewater, the plugs 34 and 35 could be oriented into their proper positionby hand with the use of suitable orienting markings on the top of theplugs. However, where generally the wellhead assembly of the presentinvention is to be positioned underwater where it is necessary to dropthe plugs 34 and 35 into place or lower them by means of a wire line, itis essential that they be provided with guide means for their properorientation. Any suitable guide means may be employed. In the event thataniobject or substance, such as a packer or a chemical, is to becirculated down the well for permanent use therein'and it is not meantto be circulated back to the surface, then it is apparent that nodiverting plugs 34 and 35 are needed in the spool piece 21 during thatoperation. Fixedly secured to the top of the Y spool piece 21 is acontrol valve 46 which is preferably of the identical design as themaster valves 18 and 18a, having dual passageways therethrough will fillopening plugs or gates therein.

When the flowlines 32 and 33 are connected to lowpressure-ratedfiowlines which extend to shore, it is necessary to provide the sideconduits 24 and 25 with suitable landing surfaces for removably seatingand securing a pair of chokes 47 and 48 therein when the presentwellhead assembly is employed on a high-pressure well. The chokes arepressure-reducing devices well known to the art and since their specificdesign and construction is a matter of choice and does not constitutepart of the present invention, they will not be further described here.The chokes are provided with fishing heads 43 and 50 whereby they may bewithdrawn from their seated position by a suitable tool. Each of theside'conduits or nipples 24 and 25 are provided with a bypass conduit 54and 55 around the chokes 47 and 48. Preferably, to facilitate the manyoperations which can be carried out with the present wellhead assembly,the conduits 54 and 55 extend from a point just above the master valve13a to just below the control valves 30 and 31. Each of the conduits 54and 55 is provided with a pair of valves 56 and 57, 58 and 59,respectively. A cross-over conduit 60 is provided which is incommunication between the two bypass con duits 54 and 55 at a pointbetween the pairs of valves therein.

The entire wellhead assembly of the present invention is preferablycovered by a fiuidtight chamber 66 to protect the component parts fromthe corrosive action of sea water and the accumulation of marine growththereon. The valves 18, 18a, 30, 31 and 46 may be either electrically,pneumatically or hydraulically actuated by any suitable valve systemwell known to the art. In this particular installation an electric cable67 is provided for conducting electric signals to energize the series ofelectrically actuated pilot valves 63-75 which control the flow of thehydraulic pressure fluid from electrically driven pumps 76 and 77. Thepressure fluid is contained in reservoirs 78 and '79.

In another arrangement of the present Wellhead as sembly, shown inFlG-URE 2, the side conduits or nipples 124 and 125 are in communicationthrough valves 119 and 120 with a tubing string 128 within the well andthe annulus 129 outside the tubing string 128, respectively. In thisarrangement, there are no vertical conduits from the well and the sideconduit or nipple 125 does not have to be a smoothly curving section ofpipe since tools or instruments can only be circulated through flowline132 and nipple 124 into the tubing string 128. However slugs ofchemicals could be injected into the well through either nipple .124 or125. The well head control maulfold system of FIGURE 2 is provided withcontrol valves 130 and 131, bypass conduits 154 and. 155, valves 156 159and bypass conduit 16%, all of these elements being similiar to theirrespective counter parts described hcreinabove 'with regard to FIGURE 1.

In some installations where it is not desired to circulate tools in thewell but merely to inject slugs of chemicals therein, the wellheadassembly may be of the type shown in FIGURE 3 which is not provided withany smoothly curving conduit but merely with a pair of nipples 224 and225 having right-angle bends in which to seat a pair of chokes 247 and248 on the downstream side of control valves 230 and 231. The nipples224 and 22s are in @6111- munication through valves 219 and 220 withindividual parallel tubing strings 233 and 239. Like the assembly ofFIGURE 1, the apparatus in FIGURE 3 is provided with bypass conduits 254and 255 having valves 256-259 therein and a bypass conduit 260.

The operation of the wellhead of the present assembly will be describedwith regard to the operation of removing the flow-control choke 47 fromthe side conduit or nipple 24 (FIGURE 1) without subjecting thelow-pressure flowline attached to flowline 32 to high well pressures.

As a first step, all flow of fluid from the well is stopped by closingvalves 30, 19a and 19, as well as valves 31, 20a and 20. Itis to beunderstood that valves 46, 56, 57, 58 and 59 are normally closed. Inorder to pump a choke retrieving tool through flowline 32 to engagechoke 47, valves 30, 56, 57, 58 and 31 would be opened. The chokeretrieving tool would be pumped through flowline 32 and valve 30 toengage the fishing head 49 of choke 47. As the choke retrieving tool ispumped into place, the fluid in front of it will pass through bypassconduit 54, crossover conduit 60, bypass conduit 55 and through controlvalve 58 to be discharged above choke 48 and thence out through valve 31and flowline 33.

After the tool is latched onto the choke, the combined tool and chokewould be returned to the starting point of the tool by reversing theflow of fluid in the abovedescribed path. Thus, fluid would be pumped inthrough flowline 33, through valve 31, valve 58, bypass line 55,cross-over conduit 60, bypass conduit 54, and thence through valve 56 orvalve 57 into the nipple 24 and through valve 30 into flowline 32. A newchoke could then be pumped through flowline 32 in a similar manner withthe fluid ahead of the choke passing through the manifold system, in themanner described hereinabove, to pass out the flowline 33. Again therunning tool could be returned to its starting point by reversing theflow of fluid from flowline 33 through the manifold and out flowline 32.Instead of pumping fluid in through flowline 33, the flowing fluidstream from the well may be utilized, if desired, for returning thetools to their starting point. For example, the choke-retrieving tooland the choke could be returned to shore, or to a production platform,by closing valve 31, opening valves 20 20a and 58 and allowing wellfluid to flow up conduit 16 through valves 20 and 20a, throughpressure-reducing choke 48, through valve 58 and bypass 55, cross-overconduit 60 and thence through valve 57 into the side nipple 24 below thechoke 47 and its running tool (not shown) attached thereto.

In another operation, various tools or other devices could be installedin the well by positioning the tool or instrument in a vertical ornear-vertical position within the side nipple 24 after the choke 47 hasbeen removed therefrom, and subsequently allowing the tool or instrumentto fall freely through the master valves 19a and 19 down the conduit andinto the tubing string (not shown) in communication therewith. Theoperation would be accomplished in the following manner. After valves 19and were closed the choke 47 would be removed from the side conduit ornipple 24 in a manner described hereinabove. The downhole tool orinstrument is then pumped through flowline 32 and valve 30 until it isseated in the nipple 24 above valve 19a. During this pumping operation,valves 30, 57, 58 and 31 are open so that fluid passes through themanifold and out the flowline 33. After the tool is in the nipple 24above the valve 19a, valves 30 and 57 are closed and valves 19 and 19aare open to allow the tool to fall freely down the tubing string. Whenit is desired to return the tool to the nipple 24 above valve 19a, thefluid coming up the conduit 15 from the well is directed through openvalves 19, 19a and 57, through cross-over conduit 60 and thence throughopen valve 59, choke 48 and open valve 31 into the flowline 33. Afterthe tool has reached its position above valve 19a in the nipple 24,valves 19a and 19 are closed and the tool may then be pumped back to aplatform by flowing the fluid in the reverse manner.

When it is desired to inject slugs of chemicals down the well, this maybe done in a manner similar to the installation of the down-the-holetools, described above. A slug of chemical would be located in thenipple 24 between the valves 30 and 19a and subsequently be allowed togravitate down the tubing string, it being assumed that the chemicalwould have a higher specific gravity than the well fluid. The presentmanifolding assembly can also be employed on a gas Well and would allowchanging of the flow control choke, down-the-hole storm chokes, wouldallow running down-the-hole pressure recorders, etc., as well asinjecting chemicals to prevent corrosion, to prevent hydrate, paraflin,and/ or asphaltine formations.

We claim as our invention:

1. A wellhead assembly connecting a pair of tubing strings handling highpressures within the well to a pair of flowlines handling fluids atlower pressures outside the well, said wellhead assembly comprising apair of flow nipples mounted on said wellhead assembly forming at leasta portion of the flowlines in fluid communication with a pair of tubingstrings within the well, at least one of said nipples beingsmoothly-curved branching upwardly and outwardly, each of said nippleshaving a'choke landing surface in the bore thereof for seating a choketherein, well control master valve means carried by said wellheadassembly on the well side of said nipples for controlling the well fluidflow therethrough, second valve means at the other ends of said nipples,bypass conduit means in fluid flow communication with each nipple aroundthe choke landing surface thereof, a pair of spaced valve means in eachof said bypass conduit means, and crossover conduit means incommunication with and between said two bypass conduit means at a pointbetween the pairs of valve means therein.

2. A wellhead assembly connecting a pair of tubing strings handling highpressures within the well to a pair of flowlines handling fluids atlower pressures outside the well, said wellhead assembly comprisingclosure means for closing the top of a well casinghead and having a pairof vertical flow conduits therethrough in communication with a pair oftubing strings within the well, a pair of flow nipples mounted on saidclosure means connecting the flow conduits of said closure means influid communication with said flowlines, at least one of said nipplesbeing smoothly-curved branching upwardly and outwardly, each of saidnipples having a choke landing surface in the bore thereof for seating achoke therein, well control master valve means carried by said wellheadassembly on the well side of said nipples for controlling the well fluidflow therethrough, second valve means at the other ends of said nipples,bypass conduit means in fluid flow communication with each nipple aroundthe choke landing surface thereof, a pair of spaced valve means in eachof said bypass conduit means, and cross-over conduit means incommunication with and between said two bypass conduit means at a pointbetween the pairs of valve means therein.

3. A wellhead assembly adapted to be secured to the top of a wellcasinghead for controlling the fluid flow from said well while providingdual conduit means permitting the entry of substances into a well aswell as the circulation of said substances therefrom, said wellheadassembly connecting a pair of tubing strings handling high pressureswithin the well to a pair of flowlines handling fluids at lowerpressures outside the well, said wellhead assembly comprising closuremeans for closing the top of a well casinghead and having a pair ofvertical flow conduits therethrough in communication with a pair oftubing strings within the well, a pair of flow nipples mounted on saidclosure means connecting the flow conduits of said closure means influid communication with said flowlines, said nipples beingsmoothly-curved branching upwardly and outwardly, each of said nippleshaving a choke landing surface in the bore thereof for seating a choketherein, well control master valve means carried by said wellheadassembly on the well side of said nipples for controlling the well fluidflow, second valve means at the other ends of said nipples, bypassconduit means in fluid flow communication with each nipple around thechoke landing surface thereof, a pair of spaced valve means in each ofsaid bypass conduit means, and crossover conduit means in communicationwith and between said two bypass conduit means at a point between thepairs of valve means therein.

4. The apparatus of claim 3 including a removably seated and latchedchoke positioned on the landing surface in the bore of each of thenipples.

5. A wellhead assembly adapted to be secured to the top of a wellcasinghead for controlling the fluid flow from said Well while providingdual conduit means permitting the entry of substances into a well aswell as the circulation of said substances therefrom, said wellheadassembly connecting a pair of tubing strings handling high pressuresWithin the well to a pair of flowlines handling fluids at lowerpressures outside the Well, said Wellhead assembly comprising closuremeans for closing the top of a well casinghead and having a pair ofvertical flow conduits therethrough in communication with a pair oftubing strings Within the Well, a pair of flow nipplesmounted on saidclosure means connecting the flow conduits of said closure means influid communication with said flowlines, each of said nipples having achoke landing surface in the bore thereof for seating a choke therein,Well control master valve means carried by said wellhead assembly on thewell side of said nipples for controlling the Well fluid flow, secondvalve means at the other ends of said nipples, bypass conduit means influid flow communication with each nipple around the choke landingsurface thereof, a pair of spaced valve means in each of said bypassconduit means, and cross-over conduit means in communication with andbetween said two bypass conduit means at a point between the pairs ofvalve means therein.

No references cited

1. A WELLHEAD ASSEMBLY CONNECTING A PAIR OF TUBING STRINGS HANDLING HIGHPRESSURES WITHIN THE WELL TO A PAIR OF FLOWLINES HANDLING FLUIDS ATLOWER PRESSURES OUTSIDE THE WELL, SAID WELLHEAD ASSEMBLY COMPRISING APAIR OF FLOW NIPPLES MOUNTED ON SAID WELLHEAD ASSEMBLY FORMING AT LEASTA PORTION OF THE FLOWLINES IN FLUID COMMUNICATION WITH A PAIR OF TUBINGSTRINGS WITHIN THE WELL, AT LEAST ONE OF SAID NIPPLES BEINGSMOOTHLY-CURVED BRANCHING UPWARDLY AND OUTWARDLY, EACH OF SAID NIPPLESHAVING A CHOKE LANDINGK SURFACE IN THE BORE THEREOF FOR SEATING A CHOKETHEREIN, WELL CONTROL MASTER VALVE MEANS CARRIED BY SAID WELLHEADASSEMBLY ON THE WELL SIDE OF SAID NIPPLES FOR CONTROLLING THE WELL FLUIDFLOW THERETHROUGH, SECOND VALVE MEANS AT THE OTHER ENDS OF SAID NIPPLES,BYPASS CONDUIT MEANS IN FLUID FLOW COMMUNICATION WITH EACH NIPPLE AROUNDTHE CHOKE LANDING SURFACE THEREOF, A PAIR OF SPACED VALVE MEANS IN EACHOF SAID BYPASS CONDUIT MEANS, AND CROSSOVER CONDUIT MEANS INCOMMUNICATION WITH AND BETWEEN SAID TWO BYPASS CONDUIT MEANS AT A POINTBETWEEN THE PAIRS OF VALVE MEANS THEREIN.